Amaya Arencibia

Aqueous heavy metals removal by adsorption on amine-functionalized mesoporous silica

Amino functional mesoporous silica SBA-15 materials have been prepared to develop efficient adsorbents of heavy metals in wastewater. Functionalization with amino groups has been carried out by using two independent methods, grafting and co-condensation. Three organic moieties have been selected to incorporate the active amino sites: aminopropyl (H(2)N-(CH(2))(3)-), [2-aminoethylamino]-propyl (H(2)N-(CH(2))(2)-NH-(CH(2))(3)-) and [(2-aminoethylamino)-ethylamino]-propyl (H(2)N-(CH(2))(2)-NH-(CH(2))(2)-NH-(CH(2))(3)-). Materials have been characterized by XRD, nitrogen sorption measurements and chemical analysis. We have found that all materials preserve the mesoscopic order and exhibit suitable textural properties and nitrogen contents to act as potential adsorbents. Metal removal from aqueous solution has been examined for Cu(II), Ni(II), Pb(II), Cd(II), and Zn(II); adsorption performances of materials prepared by the two functionalization methods have been compared. In addition, copper adsorption process has been thoroughly studied from both kinetic and equilibrium points of view for some selected materials. Aqueous Cu(II) adsorption rates show that the overall process is fast and the time evolution can be successfully reproduced with a pseudo-second-order kinetic model. Whole copper adsorption isotherms have been obtained at 25 degrees C. Significant maximum adsorption capacities have been found with excellent behavior at low concentration.

Development of high efficiency adsorbents for CO2 capture based on a double-functionalization method of grafting and impregnation

A functionalization method based on the impregnation of previously grafted pore-expanded SBA-15 is presented. The combination of tethered and mobile amino groups has led to a synergic effect, yielding samples with CO2 uptakes up to 235 mg CO2 per g (5.34 mmol CO2 per g) at 45 °C and 0.15 bar CO2 and high adsorption efficiencies.

An investigation of the textural properties of mesostructured silica-based adsorbents for predicting CO2 adsorption capacity

Among the technologies proposed to reduce greenhouse gas emissions, adsorption with porous solids has been widely studied in the past few years. Herein, up to 30 inorganic porous adsorbents have been studied, obtaining their CO2 uptake at 45 °C and ambient pressure, typical conditions of industrial post-combustion facilities after the desulphurization step. A clear relationship between CO2 adsorption capacity and the combination of surface area (SBET) and sorbent affinity towards gas molecules through C parameter was found. This study provides novel findings that allow the prediction of CO2 uptake in mesostructured silica physisorbents from their textural properties.

Magnetic, structural and surface properties of functionalized maghemite nanoparticles for copper and lead adsorption

In this study, magnetic nanocomposites were developed and used as adsorbents for lead and copper from aqueous media. Structural, surface, magnetic and textural properties of functionalized maghemite nanoparticles synthesized by alkaline co-precipitation were studied. The surfaces of the iron oxide nanoparticles (Nps) were modified with different chemical agents such as fatty and amino acids, silica (SiO2), mesoporous silica (SBA-15), hydroxyapatite, multiwall carbon nanotubes (MWCNTs) and ethylenediaminetetraacetic acid (EDTA), obtaining NPs with mean particle sizes ranging from 7 to 16 nm according to Rietveld refinement and TEM images analysis. The physicochemical surface properties of the functionalized materials were studied via zeta potential (ζ) and Fourier transform infrared (FTIR) spectroscopy. Mossbauer spectroscopy (MS) as a function of temperature and DC magnetometry were used to study the magnetic properties. The superparamagnetic relaxation was studied by MS. The resolved spectra at 20 K confirm the presence of nanomaghemite phase. Besides, the saturation magnetization varies from 12 to 62 emu g−1. A nitrogen adsorption–desorption technique was used to determine the specific surface area and to study the porous structure. The functionalized γ-Fe2O3 Nps exhibited a Brunauer–Emmett–Teller (BET) specific surface area ranging from 74 to 214 m2 g−1 and revealed remarkable uptake capacities to remove Cu(II) and Pb(II) species from aqueous solutions.

Heavy metals removal from water by adsorption on propylthiol-functionalised mesoporous silica obtained by co-condensation

Propylthiol-functionalised mesoporous silica SBA-15 prepared by co-condensation has been tested for heavy metal removal. Adsorption from aqueous solution was examined for Cu(II), Pb(II), Cd(II), and Hg(II). Adsorption isotherms were determined at 20°C and Langmuir and Freundlich models were fitted to experimental data. The results from adsorption experiments indicate that mercury is efficiently removed from water. Copper, lead and cadmium uptakes from aqueous solution are noticeable but significantly smaller than mercury removal; moreover, lead and cadmium adsorption isotherms exhibit no adsorption maximum within the investigated range of concentration. The influence of solution pH on lead adsorption was also investigated.

Monte Carlo method to explain the probabilistic interpretation of atomic quantum mechanics

Quantum mechanics description of physical and chemical systems is included in books of Physics, General Chemistry or Physical Chemistry including mathematical, graphical, and conceptual descriptions. Mathematical calculations are complex and are covered only in advanced courses. Main problem in the first degree courses is the understanding of the probabilistic interpretation of quantum mechanics. The Monte Carlo method is based on probabilistic concepts and its application to quantum calculations can be carried out quite straightforward. In this work, a simple Monte Carlo method was used to obtain a sequence of random electron coordinates according to the probability given by the wave function. Electron is seen as a shot whose appearance is only accepted and plotted when probability is high enough. Hydrogen atom was studied as it is a familiar system for most students and its description can be easily related to previous knowledge of atomic orbitals. The objective of the present work is to supply all the crucial points that students need to create their own program to plot atomic orbitals according to the above ideas. All the numerical details are indicated in order to get the proposed programming project as a simple task. Student should be able to generate random electron coordinates, to compute wave functions and probabilities, and to obtain plots according to the right probabilistic interpretation of quantum mechanics. In order to show the quantitative obtained plots some results were shown. Typical s, p, and d orbitals were obtained and compared to the usual angular and radial representation.